The invention relates to an apparatus for making a drilled hole with an undercut, particularly in a facing panel.
A device for making a drilled hole with an undercut is known. This device consists of a drilling machine having a drilling tool received in an adapter joined to the drilling machine so as to transfer torque, a supporting stand for the drilling machine having a holding means, and a bearing bush secured in the holding means, in which bearing bush a sleeve fixedly joined to the drilling machine is received and mounted so as to rotate and swivel via a swivel bearing.
To produce a drilled hole with an undercut, a device is known which has a bearing bush provided with a concave depression in which a drilling tool provided with a collar is supported and mounted so as to swivel. By swivelling out the drilling tool while simultaneously performing a stirring movement, the lateral cutting edges arranged on the drilling tool ream out an under cut in the region of the bottom of the drilled hole, into which undercut an expansible plug with an expansible sleeve can be inserted with a matching fit.
A drilled hole of this type with an undercut can also be made in a facing panel or similar structure, but there the undercut must be made very exactly, so that, when an expansible anchor is inserted and expanded. The expansion pressure that is produced by the anchor should not be too great. Too great an expansion pressure can cause a part of the facing panel to break away. To produce an exact undercut, a drilling tool that has a drilling head provided with diamond chips is used. The known devices for producing drilled holes with undercuts are inadequate for these impact-sensitive and shock-sensitive drilled holes with undercuts in thin-walled facing panels.